1. Field of the Invention
The present invention relates to an image forming apparatus used for copying machines, printers, facsimiles and so on. More specifically, the present invention relates to an image forming apparatus in which a developing device which is replenished with toner from a replenishing device is removably mounted to an apparatus body.
2. Description of the Related Art
An image forming apparatus is used for copying machines, printers, facsimiles, and multi-function machines having at least two of these functions. The uniformly charged surface of a photoreceptor drum is selectively exposed according to image information, and an electrostatic latent image is formed thereon. The electrostatic latent image is developed and a toner image is formed. More specifically, the electrostatic latent image is developed by toner which is supplied to the surface of the photoreceptor drum from a developing sleeve. The toner image is then transferred to a printing sheet to form an image. Subsequently, this unfixed toner image is fixed to the printing sheet.
The toner is stored in a container. The container is provided with the developing sleeve and a screw for stirring and transferring the toner. The container, the developing sleeve, and the screw are unitized as a developing unit. Since the toner is supplied from the developing sleeve to the photoreceptor drum where it is consumed, it is necessary to compensate for the reduction of the toner in the developing unit. Therefore, a toner replenishing mechanism for replenishing toner to the developing unit is provided. Such a toner replenishing mechanism is configured as follows. Toner stored in a toner replenishing container is transferred to a toner replenishing section while being stirred by the screw. The toner is discharged from a discharge port provided on the toner replenishing section. The toner is then replenished to the developing unit through an inlet port. The inlet port is provided on the developing unit.
Sliding shutters are provided to open and close the discharge port and the inlet port, respectively. When both shutters are moved to positions that open both of the discharge port and the inlet port, the toner is replenished to the developing unit. Immediately before the opening of the discharge port, one of the shutters is slid so as to open the discharge port in a state in which the inlet port is already opened during the mounting and demounting operation of the developing unit to the apparatus body. In this manner, the toner discharged from the discharge port is prevented from spilling without being received into the developing unit which would contaminate the interior of the apparatus. In the related art, there is an image forming apparatus including a slide plate that is urged in a direction to close a discharge port of a toner replenishing container and a slide plate urged in a direction to close an inlet port of the developing unit.
However, the apparatus in the related art is not configured to open the discharge port only when the inlet port is completely opened. Therefore, there is the possibility of contaminating the interior of the apparatus with toner when mounting and demounting the developing unit.